The present invention relates to provide a method for purging fuel vapors from a fuel vapor recovery system aboard a vehicle equipped with an engine with a hybrid valvetrain. The hybrid valvetrain is an engine in which intake valves are actuated by more than one type of device.
In U.S. Pat. No. 6,009,841, an engine with a hybrid valvetrain is disclosed in which one intake valve is actuated by a source other than a camshaft. This first intake valve is independently operable meaning that the valve opening and closing events are independent of engine crankshaft position, thus, a fully variable valve. A second intake valve is actuated by a camshaft and includes a deactivator. Operation of the second valve may be discontinued or restored within one engine cycle, termed selectable intake valve herein. The exhaust valve(s) of the hybrid valvetrain is conventionally camshaft actuated. As disclosed in U.S. Pat. No. 6,009,841, the advantage of such a system over fully camless engine operation is a lower power consumption requirement.
In U.S. Pat. No. 6,009,841, no provisions for managing fuel vapors are disclosed. Modern vehicles are equipped with fuel vapor recovery systems which necessitate purging the trapped vapors within on a regular basis. As the hybrid valvetrain engine disclosed in U.S. Pat. No. 6,009,841 operates unthrottled over much of the engine operating map, the conventional approach of relying on a depressed manifold pressure to allow the flow of purge gases through the fuel vapor canister and into the intake manifold is not effective. A method for purging a fuel vapor recovery system of an engine with a hybrid valvetrain is disclosed.
A method for purging a fuel vapor recovery system in an internal combustion engine with at least one cylinder having at least one independently operable intake valve and at least one selectable intake valve with a predetermined valve closing time are disposed is disclosed. The engine""s air intake contains a throttle valve and an intake manifold positioned between the throttle valve and both the independently operable intake valve and the selectable intake valve. An engine controller is operably connected to the engine. The vapor recovery system includes at least one valve which controls communication between the vapor recovery system and the intake manifold. The method includes steps to determine that the vapor recovery system is not operating in a purge mode and that the vapor recovery system should be purged; detect intake manifold pressure; compare the intake manifold pressure to a predetermined purge manifold pressure threshold; and if the intake manifold pressure is greater than the redetermined purge manifold pressure threshold, decrease intake manifold pressure and actuate at least one valve in the vapor recovery system to open communication between the vapor recovery system and the air intake.
A method for purging a fuel vapor recovery system in an internal combustion engine with at least one cylinder wherein at least one independently operable intake valve and at least one selectable intake valve with a predetermined valve closing time are contained is disclosed. The engine""s air intake contains a throttle valve and an intake manifold positioned between the throttle valve and both the independently operable intake valve and the selectable intake valve. An engine controller is operably connected to the engine. The vapor recovery system includes at least one valve which controls communication between the vapor recovery system and the intake manifold. The method includes steps to determine that the vapor recovery system is operating in a purge mode and that the vapor recovery system is sufficiently purged; actuate at least one valve within the vapor recovery system for closing communication between the vapor recovery system and the air intake; and increasing intake manifold pressure.
An advantage of the present invention is that a method and a system are provided for making a transition to an engine operating condition with reduced intake manifold pressure to allow a purge of the fuel vapor recovery system to occur. Proper operation of the fuel vapor recovery system, specifically purging the system, is crucial to manage fuel vapors which evaporate from the fuel in the fuel tank. If not collected and transported to the engine intake, a substantial fraction of the fuel vapors would be released and contribute to air pollution. An advantage of the fuel vapor recovery system and method to purge the system is that compliance with federal evaporative emission standards is possible for a vehicle with a hybrid electric valvetrain.